EM 1110-2-1100 (Part II)
30 Apr 02
u'max f versus K for values of QrN (river discharge model)
Figure II-6-28.
m = bank slope
W = channel width corresponding to mean water depth in channel
ε = phase lag between sea tide and bay tide
h. The inlet as a filter, flow dominance, and net effect on sedimentation processes.
(1) Introduction. As shown previously, an inlet filters some part of the ocean tide as it translates into the
bay, depending on the characteristic inlet parameters defined earlier. Keulegan and King's analytical models,
discussed earlier, assumed a sinusoidal ocean tide, and due to the nonlinear friction term (containing u2),
solutions of bay tide response implicitly contained higher-order harmonics (i.e., frequencies higher than that
of the basic ocean tide). Other studies have shown that if a variable inlet cross section or variable bay surface
area is considered, this will introduce higher-order harmonics. The forcing ocean tide, of course, is composed
of many different frequency constituents (Part II-5), so there is interest in using this information to provide
more accurate results. Also, investigators have shown that higher harmonics of current velocity (resulting
from the forcing tides) are important in relation to sediment transport and its net movement through the inlet
(King 1974; Aubrey 1986; DiLorenzo 1988). These effects are important due to the relationship of sediment
transport to velocity raised to some power, e.g., V5 (Costa and Isaacs 1977).
(2) Tidal constituents. Boon (1988) suggests that the seven tidal constituents in Table II-6-2 adequately
represent shallow-water tide distortion in inlet-basin systems. Aubrey and Friedrichs (1988) and DiLorenzo
(1988) used the amplitude of the ratio of M4 to M2 constituent amplitudes as a measure of nonlinear
distortion. Variability in the spring-neap cycle, as well as seasonal mean water level changes, cause charac-
teristic fluctuations in M4/M2.
II-6-32
Hydrodynamics of Tidal Inlets
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